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Old 23-10-2013, 02:19   #1
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First batt refit: Criticize my plan

Thanks for looking! Ive always learned a lot from reading on this site and I finally registered as I'm planning and refitting my boat to make a trip around the Gulf Coast, to the Bahamas, and back across the gulf starting next October. I've been sailing for 5 years or so, and I've been sailing very often over the last year since I got the M38. This will be my first major refitting of the boat since I've gotten it.

Context aside, I'm hoping to get some critique on the following electrical overhaul idea.

On an average full day under sail, I expect to use a max of about 240Ah per day. Right now, I've only got the 1985 Yanmar 30hp's alternator (recently installed) to recharge my batteries (2x 12v interstate SRM27). I'm not sure exactly how many amps it produces... anyone have any ideas? I figure about 40 but I dont know... I havent had a working alt till recently and am still getting familiar with it.

I'd like to build 2 battery banks. Engine start battery will be one of the current Interstate batteries (ideally, set as "1" on the battery switch), with another one stashed and charging as a backup. House batteries ("2") with 4 6v batteries producing about 200Ah each unless I can find something with more for a decent price. In a Series/Parallel setup, meaning 2 pairs of paralleled batteries connected in series, I hope to get 400Ah at 12v. I know this is less than 3 times my daily use, but I'm hoping the next part helps...

I also plan on getting a wind generator (Aerogen 6 maybe) and probably 2 solar panels at around 120 or 135 watts each. With luck, thats collectively 150-180Ah produced on a 12kt wind mostly sunny day. Plus alternator on engine running for 1 hour for another 40Ah. If I can produce approx ~150Ah per day, I can always just run the motor an extra hour if need be....

.... right? Maybe?

I need to build this system from the ground up (charge controller, wiring, mounting, etc), so any help is appreciated. Thanks a lot, and its good to finally join the community!
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Old 23-10-2013, 02:28   #2
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Re: First batt refit: Criticize my plan

As a note, I've got this fantasy of finding some kind of flexible or foldable, stowable solar panel thats not cost prohibitive or too inefficient to be worth it. The idea would be to throw it over my bimini top when I need it on a sunny day. I dont like the thought of big panels getting knocked off, bumped, or just getting in the way. I also regularly bring down my not-so-sturdy bimini and I really like the open air way its set up so I dont want to build a solid pilothouse or top to mount rigid panels on.

Anyway... thats just another wrench in the project I guess
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Old 23-10-2013, 02:41   #3
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Re: First batt refit: Criticize my plan

There are a considerable number of posts on CF on this subject as to specifics of systems and batteries.

But in very general terms I would suggest that your house bank have at least 4 times the daily Ah capacity of your stated 240Ah per day. 240Ah is a rather an excessive amount for a small cruiser. You might want to re-evaluate the amount of electricity you are using and shift to non-electric devices if possible. An average cruiser with refrig/freezer is in the 100-150AH per day range.

Then your alternator should be also capable of putting out 4 times your expected Ah usage. Unfortunately, that would be require a 1000+ amp alternator which is rather ridiculous so then another source of power besides the engine alternator such as a genset would be an option so that you could power your loads without drawing down the batteries.

Wind and solar are not really up to supply that amount of AH per day under normal circumstances. Cruisers tend to like anchoring in calm, quiet places versus places where steady winds over 10 knots can be expected all day, all night. Solar is severely limited by sun orientation on the panels and hours of cloud free skies. Swinging at anchor really degrades solar efficiency.

So, in general, I would suggest figuring out how to cut your Ah usage per day in half and/or investigating getting a genset of some sort - like the Honda 2000EU. The Honda 2000EU little unit is most popular with cruisers. That would also allow a smaller battery bank as you would not be relying solely on stored battery capacity.

Flexible/foldable solar are quite inefficient compared to rigid units and again the available amount of solar energy per day does not lend itself to using solar as a major power supply on a cruising boat. Solar does make a good alternative when in low wind anchorages. But the cost of enough solar panels to supply your stated usage would be near to what you paid for the whole boat. The cost versus wattage produced per day for solar is quite high compared to wind or genset.
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Old 23-10-2013, 03:34   #4
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Re: First batt refit: Criticize my plan

I will be interested to hear the other responses you get also.

You certainly use a lot more than we do, more than three times as much actually.

Anyway, for what it is worth we have a very old aerogen 6 and it still cranking out near to it's rated capacity. Plus it is very quiet, the only significant noise is coming in the form of a bad bearing rumble transmitting itself down the tower on which is mounted. On my fix list but a bit of a way down the list at the moment. Best of luck.

Matt

P.s. I would say welcome to cf but I don't feel I have earned that rank yet, still a newbie.
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Old 23-10-2013, 06:24   #5
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Re: First batt refit: Criticize my plan

Greetings and welcome aboard the CF, TenaciousH.
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Old 23-10-2013, 06:55   #6
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While not cheap please note that the best flexible solar panels can be more efficient than fixed panels. The best are fitted with SunPower cells. Solbian and Solara are examples. Expensive but made for the marine market and very inexpensive to install....

Disclaimer: I sell a range of boat equipment including solar panels
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Old 23-10-2013, 07:03   #7
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Re: First batt refit: Criticize my plan

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Originally Posted by TenaciousH View Post


I also plan on getting a wind generator (Aerogen 6 maybe) and probably 2 solar panels at around 120 or 135 watts each. With luck, thats collectively 150-180Ah produced on a 12kt wind mostly sunny day.
Do not rely on luck in electrical matters.

You seem to be calculating as if your bats were empty all the time and so capable of taking full output from all sources at any time.

I would rely on the genset, then on the engine alt (fitted with high cap multi stage regulator). Then I would add solar and/or wind. If sunny or windy, you can save heaps on diesel. If not sunny or windy, you still get the juice when you want and as much as you want.

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Old 23-10-2013, 07:07   #8
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Re: First batt refit: Criticize my plan

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As a note, I've got this fantasy of finding some kind of flexible or foldable, stowable solar panel thats not cost prohibitive or too inefficient to be worth it. The idea would be to throw it over my bimini top when I need it on a sunny day. I dont like the thought of big panels getting knocked off, bumped, or just getting in the way. I also regularly bring down my not-so-sturdy bimini and I really like the open air way its set up so I dont want to build a solid pilothouse or top to mount rigid panels on.

Anyway... thats just another wrench in the project I guess
These are low-cost, high efficiency, light weight flexible solar panels. They are appropriate for bimini mounting, but not for deck walk on.
100W Customized marine use semi flexible solar panel-in Solar Panel from Consumer Electronics on Aliexpress.com
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Old 23-10-2013, 07:41   #9
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Re: First batt refit: Criticize my plan

You didn't mention a Power Monitor. That would be my first addition
2. If you're usage is really 200+AH, reduce by using LED lights, low amp TV etc., more insulation in fridge etc
3. I realize that Solar is ungainly but it can be incorporated in an arch/davits that don't shade the cockpit. If you go further south than the Bahamas, you might want the shade.

With the same battery setup as you mentioned, CFL or LED lights, stereo, SSB, a 7 cu ft fridge insulated with 6"-bottom, 4" sides, and 3 " top, 250 watt solar, I could remain at anchor for weeks. The boat ranged from N. CHessapeake to Guatemala.

YMMV.
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Old 23-10-2013, 08:05   #10
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Re: First batt refit: Criticize my plan

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You didn't mention a Power Monitor. That would be my first addition YMMV.
Agreed and do this right now whilst planning the rest as it can be done in isolation but will give you accurate figures of how much you use and the improvements you make along the way with LED lights and fridge insulation etc.

Sadly whilst your alternator might be rated for say 60 amps, in practise you won't see this and what you do see quickly drops off so to charge batteries completely can literally take hours, few do. You can add a widget to make the alternator work harder, but you still have to run the main engine lightly which isn't good for a diesel.

A Honda 20i and multi stage charger will be much more efficient and far quicker. Our Honda 20i and a 40AH charger didn't even cause the genny to run at the higher load so was ultra quiet or gave the option of heating the calorifier at the same time. Only sold the Honda when we switched to solar as we only use 30 -40AH a day during the summer and that includes the fridge, lap tops and lights etc.

Final thought, batteries are big, heavy and expensive, as already suggested efforts to reduce your usage means you will need less so saving money by being able to use smaller charging systems and a smaller bank or at least not increasing it beyond 400AH.

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Old 23-10-2013, 08:20   #11
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Re: First batt refit: Criticize my plan

Welcome to the forum.

A few comments.

240AHrs is a lot for a boat your size. Look at the options to reduce this.

400AHrs of batteries is too small for your usage even given your solar and wind.
600-800AHrs is more like it.

A 40A alternator will only produce a bit less than 30A and only if your batteries will accept this.

I don't know your local conditions but 150-180AHrs sounds optimistic. With wind remember your instruments measure at the masthead. The wind generator will be lower and the flow turbulent.
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Old 23-10-2013, 09:08   #12
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Re: First batt refit: Criticize my plan

Nigel Calder was at the 2012 Annapolis Gam. Surprisingly he stated that solar was much better than wind. He said that on a recent Norwegian cruise where he was paying strict attention the solar panels put out more power than the wind generator, even at that latitude.
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Old 23-10-2013, 10:29   #13
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Re: First batt refit: Criticize my plan

First off I want to say WOW I am blown away impressed by not only the amount of support, but the quality of it. Thanks a lot everyone!

I think from these responses, I must be miscalculating the Ah I'd use on a regular day. I take pride in my boat being a "no frills" kind of vessel, with the only power-using luxuries being the fridge conversion (havent installed it yet) and the stereo, which admittedly I use very often and at volume levels that could be tempered. No windless, large size chartplotter, electric water pump, etc. With better batteries, that can be had later.

Here are some bits of how I calculated my 240Ah. These numbers are from an inexperienced electrician's light research on comparable devices, not necessarily my own equipment as observed under sail. Translation: I dont yet know what I'm talking about, but heres where I'm at at the moment.
* 60 Ah for a full 24 hr day of refrigeration @~2.5a
* 50-60Ah for 10-12 hours of stereo at medium volume @ ~5a
* 36Ah for Instrument panel (not yet installed) 20-24 hours @ 1.5 a
* 21Ah for Garmin GPS 14 hours @ 1.5a
* 30Ah for 22" flat panel screen and a throwback N64 (no moving parts) or hard drive w movies for 2 or 3 hours

The rest (Running lights, anchor lights, interior lights, all LED. VHF, cabin fans, depth sounder, and bilge) shouldnt take up more than about 40-45Ah as I understand it. My understanding, though, is likely whats at fault

All this together comes out to about 240Ah. Maybe I went too high for stereo use, refrigeration, or the instrument panel?

Paul, those flex panels look great! I know I could fabricate some fold out sleeve for 3 of them that could be stowed. I dont mean fold the panel itself, I mean... you know what I mean.

Pete and wd, I do plan on getting a controller of some kind but I dont know exactly what kind to get. Something with an easy readout separated by banks would be great... Especially one that recognizes what I'm trying to do with splitting my engine and house banks with a charging emergency battery.

Locally (I wont be here the whole trip obviously) in CC TX, we have an average wind speed of about 14-16 knots. Wind generation isnt a problem down here, which is why I'm partial to wind.
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Old 23-10-2013, 10:44   #14
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Re: First batt refit: Criticize my plan

Those numbers are a bit high.

A typical car stereo is about 1A
Instrument panel a bit less than an 1A is typical. Normally at anchor these would not be on and when sailing the movies would not be on
GPS units vary widely a B&W GPS only will be about 0.2A. A chartplotter will be much higher.(1-3A). If you have a chart plotter a more power conservative GPS for an anchor alarm.
I play movies on my 21 inch screen for about 2.5A (screen computer and amplifier), but you need to choose equipment carefully for this sort of level.
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Old 23-10-2013, 11:03   #15
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Those numbers are a bit high.

A typical car stereo is about 1A
Instrument panel a bit less than an 1A is typical. Normally at anchor these would not be on and when sailing the movies would not be on
GPS units vary widely a B&W GPS only will be about 0.2A. A chartplotter will be much higher.(1-3A). If you have a chart plotter a more power conservative GPS for an anchor alarm.
I play movies on my 21 inch screen for about 2.5A (screen computer and amplifier), but you need to choose equipment carefully for this sort of level.
And if the fridge is running 24 hrs a day to keep the food cold you have a definite problem there.
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